Job 41:1-34.

      1. leviathan--literally, "the twisted animal," gathering itself in folds: a synonym to the Thannin (Job 3:8, Margin; see Ps 74:14; type of the Egyptian tyrant; Ps 104:26; Isa 27:1; the Babylon tyrant). A poetical generalization for all cetacean, serpentine, and saurian monsters (see on Job 40:15, hence all the description applies to no one animal); especially the crocodile; which is naturally described after the river horse, as both are found in the Nile.
      tongue . . . lettest down?--The crocodile has no tongue, or a very small one cleaving to the lower jaw. But as in fishing the tongue of the fish draws the baited hook to it, God asks, Canst thou in like manner take leviathan?

JFB.